Diaphragm pump of constant pressure type

ABSTRACT

The present invention provides a diaphragm pump of constant pressure type, mainly wherein a passage tube links between said pressure discharge port and said inlet port of said pump cover body; Thereby, the extra water pressure coming from said compressed chamber can be orderly discharged through said pressure discharge port, next guided through said passage tube to reach said inlet port, then directly flowed into said low pressure chamber; Therefore, a close water circulation loop of discharge pressure is built by means of connecting said compressed chamber, said pressure discharge port, said passage tube, said inlet port and said low pressure chamber; Thus, the present invention not only provides the function of keeping constant pressure, but also completely recycles the drained water by extra water pressure without any waste in water resource; Moreover, the present invention not only has the energy-saving effect in power consumption, but also has the environment-protecting effect in reducing operation noise; Thus, it is really an innovative invention with multiple practical effect.

FIELD OF THE PRESENT INVENTION

The present invention relates to the pressurized diaphragm pump, whichbeing exclusively used in the reverse osmosis purification apparatus,particularly for the capability of discharging the exceeding waterpressure in the compressed chamber of the pressurized diaphragm pump outof its pump cover body, then directing it into the low pressure chamberby way of the inlet port; so that the water pressure of the outlet portin said pump cover body can be kept in a expected constant value.

BACKGROUND OF THE INVENTION

Currently, the pressurized diaphragm pump types used in the reverseosmosis purification apparatus, such as U.S. Pat. Nos. 4,396,357,4,610,605, 5,476,367, 5,571,000, 5,615,597, 5,626,464, 5,649,812,5,706,715, 5,791,882, 5,816,133, 6,048,183, 6,089,838, 6,299,414,6,604,909, 6,840,745 and 6,892,624 are all disclosed; The best seller ofthe pressurized diaphragm pump exclusively used in the conventionalreverse osmosis purification apparatus is shown in the FIG. 1 throughFIG. 3, comprising: a motor 10; an upper lid chassis 11, which being onthe top end of the output shaft (not shown in the figure) of said motor10, has some screw bores 12 set up on its circumference; some wobbleplates 13, which being hinged in said upper lid chassis 11, are drivenby the output shaft of said motor 10 and being transferred into axiallyreciprocating motion; a diaphragm valve frame 20, which covering on saidupper lid chassis 11, has a high pressure valve 21 embedded in thecenter of its top with some low pressure valves 22 being embedded at thebottom side of the circumference of said high pressure valve 21; and apump cover body 30; All the components aforesaid are firmly screwedtogether as a integral body by the bolts 2 running through said screwbores 12 on said upper lid chassis 11 and corresponding perforated bores36 on said pump cover body 30 (as shown in the FIG. 2).

Wherein said pump cover body 30, an inlet port 31 and an outlet port 32are contrived on both corresponding ends of its outer rim; a laddergroove 37 is circled at the bottom of its inner side such that can stayclosely with the periphery of said diaphragm valve frame 20; an annulargroove 38 facing towards said ladder groove 37 is raised in the centerof its inner side with an outlet orifice 35 perforated to conduct withsaid outlet port 32; Wherein, the top end of said annular groove 38presses closely with the periphery of said high pressure valve 21 onsaid diaphragm valve frame 20, so that a compressed chamber 34 is formedbetween the inner side of said annular groove 38 and said diaphragmvalve frame 20 as well as some low pressure chamber 33 being formedamong the outer side of said annular groove 38 and the inner side ofsaid pump cover body 30 (as shown in the FIG. 1 and the FIG. 2).

Refer to the FIG. 1 through the FIG. 3, the unfiltered feed water W,which entering said inlet port 31 of said pump cover body 30, firstreaches said low pressure chamber 33 for being increased its pressure upto 60 psi˜120 psi normal rated pressure; In said low pressure chamber33, the reciprocating axially motion of said wobble plates 13 driven bysaid motor 10 will force all said low pressure valves 22 movementorderly for suction and compression of said feed water W so as toincrease to water pressure; The pressurized feed water W flows into saidcompressed chamber 34 through high pressure valve 21, next passes saidoutlet orifice 35 of said annular groove 38, then directly drains out ofthe pressurized diaphragm pump from said outlet port 32 of said pumpcover body 30; Said pressurized feed water W with water pressure, whichconforms to the normal rated water pressure of the reverse osmosissemi-permeable membrane filter cartridge or module (not shown in thefigure, hereinafter called RO membrane), is output and supplied to thereverse osmosis purification apparatus for filtration and purification.

Currently, all the various RO membrane in the market have markindicating the normal rated water pressure and the service life indifferent specification basically depending on the quantity of waterbeing filtrated; For example, the RO membrane with less filtratingquantity of water might have mark indicating that the quantity of theproduct filtrated drinking water per day under normal rated waterpressure of 60 psi is 10 gallons, and the total filtrating quantity ofwater in durable service life is 1500 gallons; Hence, the output waterpressure of the pressurized diaphragm pump to be used in match with suchRO membrane is better not to exceed 60 psi, otherwise it will quicklyshorten the service life of said RO membrane. For some non-residentialplaces, which demand much more quantity of product water, the ROmembrane with ample specification will be adopted for having relativehigh normal rated water pressure up to 100 psi˜120 psi and the quantityof the product filtrated drinking water per day is up to 160 gallons; Inthis case, the output water pressure of the pressurized diaphragm pumpto be used in match with such RO membrane is better to reach 120 psi.Therefore, all the domestic or overseas manufacturers of the pressurizeddiaphragm pump will specify their product with normal rated waterpressure of 120 psi to meet different specifications of the RO membrane.

However, the way described above has serious drawback in discrepancy ofthe pressurized diaphragm pump and the RO membrane, namely the normalrated water pressure of the RO membrane is 60 psi or 70 psi and that ofthe pressurized diaphragm pump is 120 psi; Under such circumstance, thefibrous filter material in the RO membrane will be torn so that theinterstices in between become bigger gradually due to constant highpressure stress; Thereby, not only the function in filtering theturbidity of impurities is diminished, but also the durable service lifeis shortened; Thus, the consumer becomes a victim owing to the frequencyof replacing new RO membrane is increased in consequence of theseadverse effects aforesaid. Moreover, as shown in the FIG. 3, the ROmembrane will be gradually fouled by the filtered impurities duringfiltering service time; Hence the pressurized water coming from thecompressed chamber 34 in the pump cover body 30 of the pressurizeddiaphragm pump can not completely flow into said pump cover body 30 andresulting in backwater pressure against the diaphragm valve frame 20;Thereby, the leakage will happens between said pump cover body 30 andsaid diaphragm valve frame 20 due to constant backwater pressure inlong-term; Again, the consumer becomes a victim out of luck owing to thetiming of replacing said entire pressurized diaphragm pump is earlierthan the marked expiry time in consequence of the leakage aforesaid.

The drawbacks aforesaid include all the conventional pressurizeddiaphragm pumps of USA patents disclosed; Since 1985 the pressurizeddiaphragm pump was invented, there was not any contrivance to remedy thedrawbacks aforesaid for a long time until recently three years when newcontrivance of the pressurized diaphragm pump with design in regulatingthe exceeding high water pressure in the compressed chamber 44 beingintroduced into market; the structure is as shown in the FIG. 4 throughthe FIG. 7, A pressure discharge cavity 47 is formed in the center ofthe compressed chamber 44, which being in the inner side of the pumpcover body 40, and a pressure adjusting base 50 is built in the topcenter of the outer side of said pump cover body 40, wherein: In saidpressure discharge cavity 47, a pressure discharge orifice 48 isperforated at the center at its bottom side, and a pressure dischargechannel 49 is perforated at it lateral side such that the end conductsto the low pressure chamber 43; For said pressure adjusting base 50,pressure adjusting screw 51 is inset in its center such that the endinternally with a compressed spring 52 and a baffle rod 53 protrudinginto said pressure discharge cavity 47; Said baffle rod 53 stays closelyagainst said pressure discharge orifice 48 of said pressure dischargecavity 47 by the spring force of said compressed spring 52. Refer to theFIG. 8 and FIG. 9, when the feed water W flows into said low pressurechamber 43 through said inlet port 41, its pressure will be increased bythe action of the wobble plate 13; Then, said feed water W flows intosaid compressed chamber 44 through said low pressure valve 22 and highpressure valve 21; Finally, said feed water W flows for the RO membranewith normal rated pressure through said outlet orifice 46 and outletport 42; Under normal rated pressure, said baffle rod 53 will stayclosely and block said pressure discharge orifice 48 of said pressuredischarge cavity 47 by means of the spring force of said compressedspring 52 acting on said baffle rod 53; Therefore, all the pressurizedfeed water W from said compressed chamber 44 will output out of saidpump cover body 40 through outlet orifice 46 and outlet port 42 (asshown in the FIG. 8); When the water pressure in said compressed chamber44 exceeds the normal rated pressure, the water pressure will push saidbaffle rod 53 off said pressure discharge orifice 48 to allow the extrawater pressure feedback into said low pressure chamber 43 through saidpressure discharge orifice 48 and pressure discharge cavity 47 as wellas pressure discharge channel 49 (as shown in the FIG. 9) so as toregulate the water pressure in said compressed chamber 44. However, theconventional pressurized diaphragm pump of internal pressure regulatingtype actually does not discharge the internal extra water pressure outof itself; It only constantly circulates the extra water pressure amongsaid compressed chamber 44 and said low pressure chamber 43; So, theproblem of the holding and exceeding of the water pressure in saidcompressed chamber 44 will happen after said pressurized diaphragm pumprunning for a period of time.

Accordingly, after the inventor of the present invention finds out thedrawback aforesaid, he renders a remedy contrivance and patentapplication to the IPO of Taiwan at Jan. 14 of 2003 as well as beingallowanced and granted the patent number 225942 (publication number:595656) in file. Its structure is as shown in the FIG. 10 through 14: Inthe pressure adjusting groove 68, which being indented at the outer topof the pump cover body 60 with facing inwards of the annular groove 65,a pressure discharge orifice 67 is perforated at its bottom side withfacing towards said annular groove 65; For said pressure adjustinggroove 68, an adjusting screw 200 is inset in said pressure adjustinggroove 68 such that the end internally with a compressed spring 201 anda baffle lump 202; Wherein, said baffle lump 202 stays closely againstsaid pressure discharge orifice 67 by the spring force of saidcompressed spring 201.

Refer to the FIG. 11 and the FIG. 13, when the water pressure of thepressurized feed water W from said compressed chamber 64 is under normalrated pressure, said baffle lump 202 can not be pushed off and willstill block said pressure discharge orifice 67; Therefore, all thepressurized feed water W from said compressed chamber 64 will output outof said pump cover body 60 through outlet orifice 66 and outlet port 62(as shown in the FIG. 11); When the water pressure in said compressedchamber 64 exceeds the normal rated pressure, the water pressure willpush said baffle lump 202 off said pressure discharge orifice 67 toallow the extra water pressure discharge out of said pump cover body 60through said pressure discharge orifice 67 and pressure discharge port69 (as shown in the FIG. 13); When the water pressure in said compressedchamber 64 descends back below the normal rated pressure, said bafflelump 202 will bounce back by the spring force of said compressed spring201 to return closely and block said pressure discharge orifice 67 toinhibit the extra water pressure discharge out so as to keep the waterpressure in said compressed chamber 64 in the range of normal ratedwater pressure (as shown in the FIG. 11); Therefore, the aforesaidpressurized diaphragm pump contrived by the identical inventor of thepresent invention is a real effective remedy in regulating the exceedingwater pressure as well as discharging the extra water pressure out.Moreover, in order to prevent the water drained out of said pressuredischarge port 69 from spilling everywhere, a water pipe P sleeves onsaid pressure discharge port 69 so as to guide the drained water intothe water container (as shown in the FIG. 14).

Because the aforesaid pressurized diaphragm pump contrived by theidentical inventor of the present invention can completely meet thenormal rated water pressure in all kinds of the RO membrane as well asfree the consumer from frequently replacing said RO membrane and saidpressurized diaphragm pump, it received popularly good feedback commentsafter being introduced in the market. But, said applicant is notsatisfied with this achievement, he keeps constantly contemplation,research and study as well as attempts anxiously to breakthrough inorder to reach better condition; Thereby, he finds out some issues to beimproved as below:

1. Although the extra water, which being drained out of the pump coverbody 60 from the pressure discharge port 69, can be guided into ageneral water container for collecting to reuse, it causes the useranother boring matter in need of preparing water container or burdensomecollecting water; For convenience, most of the consumers will select todump it out and resulting in wasting water resource.

2. The water running noise accompanying with the draining of the extrawater out of the pump cover body 60 from the pressure discharge port 69will interfere with the internal calmness and peace of the residentialenvironment.

SUMMARY OF THE INVENTION

A main object of the present invention is to provide a diaphragm pump ofconstant pressure type, mainly wherein a passage tube links between saidpressure discharge port and said inlet port of said pump cover body;Thereby, the extra water pressure coming from said compressed chambercan be orderly discharged through said pressure discharge port, nextguided through said passage tube to reach said inlet port, then directlyflowed into said low pressure chamber; Therefore, a close watercirculation loop of discharge pressure is built by means of connectingsaid compressed chamber, said pressure discharge port, said passagetube, said inlet port and said low pressure chamber; Thus, it not onlysaves the drain water by the extra water pressure from directing intothe other prepared container, but also solves the inconvenience andwasting in reluctantly recycling from the side effect of suchinconvenience.

Another object of the present invention is to provide a diaphragm pumpof constant pressure type, wherein the extra water pressure willdirectly flow into said inlet port to converge with the input waterpressure; Thereby, the total input water pressure of the pressurizeddiaphragm pump is increased so as to save the motive power of the motorindirectly as well as achieving the energy-saving effect of saving powerconsumption.

The other object of the present invention is to provide a diaphragm pumpof constant pressure type, wherein a circulating buffer annular grooveis indented around said pressure discharge orifice at the outercircumference of the intersection of said pressure adjusting groove andsaid pressure discharge orifice; Thereby, the extra water pressure beingforced to flow into said circulating buffer annular groove beforerunning into said pressure discharge port; Thus, it has the effect inreducing the operation noise of the pressurized diaphragm pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the perspective exploded view of the conventional pressurizeddiaphragm pump.

FIG. 2 is the first illustrative view showing the cross-section of thepump cover body in the conventional pressurized diaphragm pump.

FIG. 3 is the second illustrative view showing the cross-section of thepump cover body in the conventional pressurized diaphragm pump.

FIG. 4 is the first illustrative view showing the perspective of thepump cover body in the conventional pressurized diaphragm pump ofinternal pressure regulating type.

FIG. 5 is the second illustrative view showing the perspective of thepump cover body in the conventional pressurized diaphragm pump ofinternal pressure regulating type.

FIG. 6 is a sectional view taken along the direction indicated by a line6-6 as shown in FIG. 5.

FIG. 7 is a sectional view taken along the direction indicated by a line7-7 as shown in FIG. 5.

FIG. 8 is the first illustrative view showing the operation of the pumpcover body in the conventional pressurized diaphragm pump of internalpressure regulating type.

FIG. 9 is the second illustrative view showing the operation of the pumpcover body in the conventional pressurized diaphragm pump of internalpressure regulating type.

FIG. 10 is the illustrative view showing the perspective of the pumpcover body in the conventional pressurized diaphragm pump of externalpressure regulating type.

FIG. 11 is a sectional view taken along the direction indicated by aline 11-11 as shown in FIG. 10.

FIG. 12 is a sectional view taken along the direction indicated by aline 12-12 as shown in FIG. 10.

FIG. 13 is the illustrative view showing the operation of the pump coverbody in the conventional pressurized diaphragm pump of external pressureregulating type.

FIG. 14 is the illustrative view showing the cross-section of the pumpcover body in the conventional pressurized diaphragm pump of externalpressure regulating type.

FIG. 15 is the perspective exploded view of the present invention.

FIG. 16 is the first illustrative view showing the perspective of thepump cover body of the present invention.

FIG. 17 is the second illustrative view showing the perspective of thepump cover body of the present invention.

FIG. 18 is a sectional view taken along the direction indicated by aline 18-18 as shown in FIG. 16.

FIG. 19 is a sectional view taken along the direction indicated by aline 19-19 as shown in FIG. 16.

FIG. 20 is the first illustrative view showing the operation of thepresent invention.

FIG. 21 is the second illustrative view showing the operation of thepresent invention.

FIG. 22 is the first illustrative view showing the operation of thebackflow buffer annular groove contrived in the pressure adjustinggroove of the present invention.

FIG. 23 is the second illustrative view showing the operation of thebackflow buffer annular groove contrived in the pressure adjustinggroove of the present invention.

FIG. 24 is the elevation view of the pump cover body in anotherembodiment of the present invention.

FIG. 25 is a sectional view taken along the direction indicated by aline 25-25 as shown in FIG. 24.

FIG. 26 is a sectional view taken along the direction indicated by aline 25-25 as shown in FIG. 24 with another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Refer to the FIG. 15 through the FIG. 21, the first embodiment of thepresent invention comprises: a motor 10; an upper lid chassis 11, whichbeing on the top end of the output shaft (not shown in the figure) ofsaid motor 10, has some screw bores 12 set up on its circumference; somewobble plate 13, which being hinged in said upper lid chassis 11, aredriven by the output shaft of said motor 10 and being transferred intoaxially reciprocating motion; a diaphragm valve frame 20, which coveringon said upper lid chassis 11, has a high pressure valve 23 embedded inthe center of its top with some low pressure valves 22 being embedded atthe bottom side of the circumference of said high pressure valve 23; anda pump cover body 70; All the components aforesaid are firmly screwedtogether as a integral body by the bolts 2 running through said screwbores 12 on said upper lid chassis 11 and corresponding perforated bores701 on said pump cover body 70 (as shown in the FIG. 15).

Wherein said pump cover body 70, an inlet port 71 and an outlet port 72are contrived on both corresponding ends of its outer rim; a laddergroove 702 is circled at the bottom of its inner side such that can stayclosely with the periphery of said diaphragm valve frame 20; an annulargroove 75 facing towards said ladder groove 702 is raised in the centerof its inner side with an outlet orifice 76 perforated to conduct withsaid outlet port 72; Wherein, the top end of said annular groove 75presses closely with the periphery of said high pressure valve 23 onsaid diaphragm valve frame 20, so that a compressed chamber 74 is formedbetween the inner side of said annular groove 75 and said diaphragmvalve frame 20 as well as some low pressure chamber 73 being formedamong the outer side of said annular groove 75 and the inner side ofsaid pump cover body 70 (as shown in the FIG. 17 and FIG. 18). In thepressure adjusting groove 78, which being indented at the outer top ofthe pump cover body 70 with facing inwards of the annular groove 75, apressure discharge orifice 77 is perforated at its bottom side withfacing towards said annular groove 75; For said pressure adjustinggroove 78, an adjusting screw 80 is inset in said pressure adjustinggroove 78 such that the end internally with a compressed spring 81 and abaffle lump 82; Wherein, said baffle lump 82 stays closely against saidpressure discharge orifice 77 by the spring force of said compressedspring 81 (as shown in the FIG. 18). Wherein, a passage tube 90 linksbetween said pressure discharge port 79 and said inlet port 71 of saidpump cover body 70 such that said passage tube 90 and said inlet port 71being screwed to a three-way manifold T (as shown in the FIGS. 16 and19); By means of connecting said compressed chamber 74, said pressuredischarge port 79, said passage tube 90, said inlet port 71 and said lowpressure chamber 73, a close water circulation loop of dischargepressure can be built.

Refer to the FIGS. 20 and 21, when the water pressure of the pressurizedfeed water W from said compressed chamber 74 is under normal ratedpressure, said baffle lump 82 can not be pushed off and will still blocksaid pressure discharge orifice 77; Therefore, all the pressurized feedwater W from said compressed chamber 74 will output out of said pumpcover body 70 through outlet orifice 76 and outlet port 72 (as shown inthe FIG. 20); When the water pressure in said compressed chamber 74exceeds the normal rated pressure, the water pressure will push saidbaffle lump 82 off said pressure discharge orifice 77 to allow the extrawater pressure discharge out of said pump cover body 70 through saidpressure discharge orifice 77 and pressure discharge port 79; Then, theextra water pressure will directly flow into said low pressure chamber73 in said pump cover body 70 by way of said three-way manifold T, whichconnecting both of said passage tube 90 and said inlet port 71 (as shownin the FIGS. 21 and 17); Simultaneously, the input water pressure comingfrom the other inlet orifice of said three-way manifold T will joinswith said extra water pressure coming from said passage tube 90 andconverges together to flow into said low pressure chamber 73 in saidpump cover body 70. In other words, if the input water pressure of thepump cover body 70 is 50 psi, the normal rated water pressure of theproduct water W is 80 psi, and the water pressure in said compressedchamber 74 reaches 90 psi, the extra water pressure is 10 psi (90 psi−80 psi =10 psi); Then, said 10 psi extra water pressure will runthrough said passage tube 90 and converges with said 50 psi input waterpressure becoming 60 psi (50 psi +10 psi =60 psi); Namely, the power ofsaid motor 10 needs to supply water pressure in 60 psi is onlyequivalent to supply water pressure in 50 psi, means for saving 10 psiconverting into less relative power consumption; As long as any extrawater pressure being discharged and circulated to said inlet port 71,the energy-saving is effected; For long-term accumulation of said savingenergy, it becomes a considerable figure; Moreover, not only the servicelife of said motor 10 is prolonged due to running in less powerconsumption, but also the durable service life of said RO membrane isextended owing to the output water pressure from said pump cover body 70being always kept in constant; All these triple advantages are thedesirable merits of the present invention to be praised.

When the water pressure in said compressed chamber 74 descends backbelow the normal rated pressure, said baffle lump 82 will bounce back bythe spring force of said compressed spring 81 to return closely andblock said pressure discharge orifice 77 to inhibit the extra waterpressure discharge out so as to keep the water pressure in saidcompressed chamber 74 in the range of normal rated water pressure (asshown in the FIG. 20).

Refer to the FIG. 22 and the FIG. 23, a circulating buffer annulargroove 781 is indented around said pressure discharge orifice 77 at theouter circumference of the intersection of said pressure adjustinggroove 78 and said pressure discharge orifice 77; Wherein, the lateralside of said circulating buffer annular groove 781 and said pressuredischarge port 79 is conducted each other, so that the extra waterpressure coming from said pressure discharge orifice 77 being forced toflow into said circulating buffer annular groove 781 before running intosaid pressure discharge port 79 (as shown in the FIG. 23); Thus, it hasthe effect in reducing the noise of running water.

The second embodiment of the present invention is shown in the FIG. 24through the FIG. 26. Wherein said passage tube 100 connecting betweensaid pressure discharge port 79 and said inlet port 71 of said pumpcover body 70 is an unitary integral body being molded together withsaid pump cover body 70.

In conclusion, the present invention really provides the function ofkeeping constant pressure to conform with the normal rated waterpressure of the RO membrane; Besides, the power consumption of thepresent invention is less than that of all the conventional pressurizeddiaphragm pumps; Moreover, the present invention not only has theenergy-saving effect in power consumption, but also has theenvironment-protecting effect in reducing operation noise; Thus, it isreally an innovative invention to conform to the industrial application.

1. A diaphragm pump of constant pressure type, which comprises: a motor;an upper lid chassis, which being on the top end of the output shaft ofsaid motor and has some screw bores set up on its circumference; threewobble plates, which being hinged in said upper lid chassis and aredriven by the output shaft of said motor and being transferred intoaxially reciprocating motion; a diaphragm valve frame, which covering onsaid upper lid chassis and has a high pressure valve embedded in thecenter of its top with some low pressure valves being embedded at thebottom side of the circumference of said high pressure valve; and thepump cover body, having an inlet port and an outlet port are contrivedon both corresponding ends of its outer rim; a ladder groove is circledat the bottom of its inner side; an annular groove facing towards saidladder groove is raised in the center of its inner side with an outletorifice perforated to conduct with said outlet port; Wherein, the topend of said annular groove presses closely with the periphery of saidhigh pressure valve on said diaphragm valve frame, so that a compressedchamber is formed between the inner side of said annular groove and saiddiaphragm valve frame as well as some low pressure chamber being formedamong the outer side of said annular groove and the inner side of saidpump cover body; In the pressure adjusting groove, which being indentedat the outer top of the pump cover body with facing inwards of theannular groove, a pressure discharge orifice is perforated at its bottomside with facing towards said annular groove; An adjusting screw isinset in said pressure adjusting groove such that the end internallywith a compressed spring and a baffle lump; Wherein, a passage tubelinks between said pressure discharge port and said inlet port of saidpump cover body such that said compressed chamber, said pressuredischarge port, said passage tube, said inlet port and said low pressurechamber building a close water circulation loop of discharge pressure.2. A diaphragm pump of constant pressure type as recited in the claim 1,wherein said passage tube is a bendable tube with flexibility.
 3. Adiaphragm pump of constant pressure type as recited in the claim 1,wherein a circulating buffer annular groove is indented around saidpressure discharge orifice at the outer circumference of theintersection of said pressure adjusting groove and said pressuredischarge orifice; And, the lateral side of said circulating bufferannular groove and said pressure discharge port is conducted each other.4. A diaphragm pump of constant pressure type as recited in the claim 1,wherein said passage tube is an unitary integral body being moldedtogether with said pump cover body.
 5. A diaphragm pump of constantpressure type as recited in the claim 2, wherein said passage tube andsaid inlet port being screwed to by a three-way manifold T.